1. Field of the Invention
This invention relates to a method of communicating data from a server computer to a client computer.
2. Related Art
The Quality of Service (QoS) provided by operators of communications networks and systems is very important, especially in sectors for which a reliable, high-speed supply of information is required e.g. banking, share dealing, etc. The increase in the use of multimedia communications over computer networks, for example audio and video streaming, television multicasting and broadcasting, etc. will also increase the difficulty involved in supplying these services with an acceptable QoS to all users due to the high bandwidths required and the real-time nature of the data. While it may be possible to meet the desired QoS targets by increasing network capacity, i.e. increasing the capacity of transmission links and increasing the throughputs of switches and routers, this will necessitate significant capital expenditure and this investment may make the costs of the supplied services prohibitively high. It is clear that there would be significant advantages if services having a given QoS could be supplied without needing to make network investments of such an extensive nature.
One significant example of the levels of network resources required to provide guaranteed QoS levels is demonstrated by connection-based networks and connection-less networks. An example of a connection-based network is the public switched telephone network (PSTN) where a connection is established by the dialling of the required telephone number. An example of a connection-less network is the Internet, where data packets are routed by the network to their destination, the user having no control over the route taken by the individual packets. The drawback of establishing a connection is that, generally, a high price must be paid in order to maintain the connection and thus guarantee delivery of the information, whereas the transmission of a stream of packets in a connection-less manner may fail due to changes in the intermediate network elements, either due to equipment failure or network congestion. Disruption to the stream of packets is a lesser problem if, for example, a text file is being downloaded from a server computer. However, if real-time data, such as video or audio, is to be transmitted then the disruption of a packet stream, so that packets arrive out of order or at a slower rate than is required for data playback, may have serious repercussions. Accordingly, especially with regard to computer communications, there is a desire to attain the quality of service that is provided by connection-based transmission methods, without the additional cost that is incurred by setting up a connection.